1. Technical Field of the Invention
The present invention relates generally to electronic devices with protective housings or cases. More particularly, the invention relates to an electronic device that includes a printed circuit board, a housing in which the printed circuit board is accommodated, a cover, and a connector. The housing has an improved structure that ensures a high rigidity of the housing and easy assembly of the electronic device.
2. Description of the Related Art
Japanese Unexamined Patent Publication No. 2003-229678 discloses an electronic device that has a housing accommodating a printed circuit board on which a connector is disposed.
The electronic device is an ECU (Electronic Control Unit) for an engine of an automotive vehicle. The ECU is shown in FIGS. 3A and 3B with a reference numeral 90 assigned thereto.
FIG. 3A is an exploded perspective view of the ECU 90. As shown in the figure, the ECU 90 includes a printed circuit board 1, a housing 2 designed to accommodate the printed circuit board 1, and a cover 3. The printed circuit board 1 has electronic components (not shown) mounted thereon. The housing 2, which is in a box-like shape, has an end opening 2h. The cover 3 has a flat-plate like shape with an aperture 3h formed therein. Both of the housing 2 and the cover 3 are fabricated from resin for weight saving. The ECU 90 further includes a connector 1c disposed on the printed circuit board 1 to connect the printed circuit board 1 with external devices or circuits. In addition, a nameplate 4 is attached on the upper wall of the housing 2.
FIG. 3B is a partially cross-sectional side view of the ECU 90. The cover 3 has, as shown in the figure, an outer periphery 3g thereof fit in the end opening 2h of the housing 2 to cover the end opening 2. A front end of the connector 3c is exposed through the aperture 3h of the cover 3 outside the housing 2, while a rear end of the same faces the end wall of the housing 2.
The ECU 90 has the deficiencies that are illustrated in FIGS. 4A, 4B, and 4C.
First, as shown in FIG. 4A, the resin-fabricated housing 2 may become deformed with the front end of the top wall thereof being flexed inwardly. In such a case, when the cover 3 is put into the end opening 2h of the housing 2 for assembly, an upper portion of the outer periphery 3g of the cover 3 will be obstructed by the front end of the top wall of the housing 2, so that the cover 3 can not be smoothly fitted into the end opening 2h. 
Secondly, when an external mating connector is improperly plugged into or out from the connector 1c, an upward or downward unnecessary torque is, as shown in FIG. 4B, applied to the connector 1c. Such a torque causes stress on the printed circuit board 1, so that the printed circuit board 1 can become deformed, resulting in a circuit failure.
Finally, as shown in FIG. 4C, when the nameplate 4 is attached to one side wall of the housing 2, a stress in the direction of the outline arrow is applied to the side wall. Such a stress may cause the side wall to be flexed inwardly, so that the side wall depresses the electronic components mounted on the printed circuit board 1, resulting in a circuit failure.